Walnut ink is a natural dye obtained from the green husk of walnuts, mainly from the common walnut tree. It has long been used to dye wood, leather, and textiles, as well as in painting and calligraphy.
Artists such as Rembrandt and Pierre Soulages frequently used it in their work.
The final result of this recipe will be (very) slightly different from the “walnut ink” you can find commercially. The reason is simple: the walnut ink sold in supermarkets and DIY stores is actually Cassel extract, derived from lignite, a fossil sediment of organic origin.
It is, of course, cheaper to produce on an industrial scale than real walnut ink, and the result is almost identical. This is why it is sold as a substitute for true walnut ink.
First, separate the walnut husks from the nuts themselves using a knife, if you collected them whole.
Cut the walnut husks into small pieces using the knife.
Place the pieces of walnut husk into a pot.
Cover the walnut husks with water.
Test the walnut stain regularly while it’s cooking.
The more the water evaporates, the darker the shade becomes. Adjust the cooking time to achieve the shade you want.
Don’t wait for all the water to evaporate: add more if needed to prevent the mixture from sticking to the bottom of the pot.
You can test your walnut stain as you go on a sheet of paper, to check whether the color suits you.
Once the cooking is finished, let the mixture cool at room temperature.
Pour the liquid into a container, filtering it through a fine sieve to remove the larger residues.
Pour the liquid into a new container, filtering it a second time through a clean cloth to obtain a perfectly clear ink, free of any impurities.
